It is often desirable to machine thermosetting laminate materials into pistol grips and knife handles because such materials are durable, lightweight, and moisture resistant. Laminate materials are mechanically and dimensionally stable and can be machined to tight tolerances. Such materials are amenable to being milled and carved, enabling textures to be added to their outer surfaces. Furthermore, machining of a laminate material consisting of layers having different colors enables desirable aesthetic effects to be created by exposing different colored layers in different locations on the material.
A very popular and versatile example of one such thermosetting laminate material is G-10/FR-4. The FR-4 version of G-10 is fire retardant. It is a high-pressure thermoset plastic laminate consisting of multiple layers of woven fiberglass mesh cloth impregnated with an epoxy resin binder. The sheets may be of the same color. Alternatively, sheets of multiple colors can be used to create the final product. The epoxy resin imparts the color to the sheets, and may provide additional color variety. The actual cloth can also be of different colors.
G-10/FR-4 has been predominantly used in relatively thin sheets as the insulating substrate for the vast majority of rigid printed circuit boards. G-10/FR4 is also used in a wide variety of other electrical and mechanical applications, including structural supports, buss bars, mechanical insulation, gears, test fixtures, washers, spacers, and tight tolerance machined parts for electromechanical assemblies. More recently, thicker sheets of G-10/FR-4 have been used to produce knife handles and pistol grips. The use of this material in these two new applications is rapidly growing in popularity.
Production of the G-10/FR-4 material starts with the cloth sheets pre-impregnated with a resin material. These sheets are loaded onto a staging table layer by layer to achieve the desired thickness and color pattern of the final sheet of material. The stacked layers then are loaded into a press between two flat platens. Utilizing high heat and high pressure, the two platens of the press form the sheets and layers together into one thicker sheet of material via polymerization. The material now consists of several layers (and colors if layers having different colors have been used). The standard method of production produces only flat, horizontally stacked layers one on top of the other. The material is typically then cut to the desired size for the finished product in which it will be used.
One of two types of press cycles is typically used to produce G-10/FR-4 material. The first cycle type is a two temperature step, two pressure step process shown in FIG. 1A. The platens are initially heated to 140° C. before they contact the sheets, then raised to the temperature of 185° C., and then gradually returned to ambient temperature. Kiss pressure is initially applied, then the pressure is increased to 400+/−50 psi, and then the pressure is lowered to 40+/−10 psi.
The second press cycle type is a one temperature step, two pressure step process shown in FIG. 1B. The platens are initially heated to 185° C. before they contact the sheets and are maintained at that temperature until they are gradually returned to ambient temperature. Kiss pressure is initially applied, then the pressure is increased to 400+/−50 psi, and then the pressure is lowered to 40+/−10 psi.
Regardless of the type of press cycle chosen, the heating rate of the material between 70° C. and 140° C. should be maintained at 1-3° C./minute, with 1.5-2.5° C./minute being preferable. The temperature of the material must be above 170° C. for at least 40 minutes to enable the epoxy resin to fully cure. The pressure should be kept below 100 psi while the material cools to ambient temperature. The cooling rate of the material should be kept below 2.5° C./minute while the temperature of the material exceeds 100° C. in order to avoid introducing twist.
An example of a pistol grip achieving desirable aesthetic effects by using G-10 material is the Diamond Backs USMC Camo G10 manufactured by VZ Grips of Tallahassee, Fla. This pistol grip is made by forming the G-10 from a cloth sheet with different colors or patterns printed on it before the sheet is impregnated with resin. The G-10 is then is milled to produce a highly slip resistant outer surface. The edges are also milled and through holes are bored so the pistol grip fits the frame of a M1911 pistol and can be secured to the frame with grip screws. This technique only imparts different colors or patterns to a single layer. While it provides a desirable aesthetic effect, it does not expose different color layers at different depths.
An example of a knife handle material achieving desirable aesthetic effects by exposing different colored layers in different locations on G-10 material is the 3DG10-130-RBK available from CKK Industries, Inc. of Haralson, Ga. This knife handle material is a two-color laminated G-10 material. It can be carved, milled, or edge-filed to expose different color layers in different locations and shape the material to receive a knife blade.
However, there are limitations to the types of aesthetic effects that can be achieved, particularly if a flat outer surface is desired. This is the case because all layers of conventional G-10 material are horizontally stacked in parallel planes. As a result, a flat surface either is limited to a single color if cut parallel to the G-10 layers or a woodgrain-like appearance if cut at an angle to the G-10 layers. Other limited patterns are provided if the surface has a non-flat contour, revealing the layers in different but limited ways.
It is therefore an object of this invention to provide a laminate material having a decorative appearance that can be machined into sturdy and attractive pistol grips and knife handles having predominantly flat surfaces.